Troubles with new PCB

Rashid Peralta

Other Parts Discussed in Thread: ADS1298, ADS1296

A time ago I designed the next PCB in order to test the ADS1298, it worked well as I expected but there was a problem, the voltage reference generated was nos appropriate for my purposes so I designed a new PCB which implements an adequate voltage reference to use as a virtual ground for the input signals as shown here

I have been testing this new PCB with the same configurations and connections for SPI communications than the first PCB I mentioned, but output data at DOUT appears to be 0 without changes, I have checked connections on PCB and everything looks fine, I would appreciate if someone tells me the problem on this design or something I am missing.

If someone has an schematic to illustrate the appropriate way to test the ADS1298 that would be great.

Regards,

Rashid

over 14 years ago

0 Tom Hendrick over 14 years ago

TI__Guru**** 182881 points

Hi Rashid,

Welcome back! Could you possible zip up these screen capture and post them again? The resolution of the captures makes it difficult to see the connections/component values you've used.

0 Rashid Peralta over 14 years ago in reply to Tom Hendrick

Prodigy 130 points

Hi Tom,

Here are the screen captures where PCB1.jpg is the first PCB design, which worked and PCB2.jpg is the second design which is having troubles. As well I am attaching the schematic files in case they were useful. Thanks!

Regards,

Rashid

3051.Troubles_PCB.zip

0 Tom Hendrick over 14 years ago in reply to Rashid Peralta

TI__Guru**** 182881 points

Hi Rashid,

Nothing in your schematic jumps out at me as being 'wrong' - I see where you created the +1.2V for use as the (-) input to the ADS1298 and added the jumper for START. As long as that is pulled high or grounded with the START command used, it should work. Have you verified the voltages at all the power pins? Are you able to read and write to the various registers?

0 Rashid Peralta over 14 years ago in reply to Tom Hendrick

Prodigy 130 points

Hi Tom,

I have measured all at all pins on ADS1296 and there are strange voltages on some of them, for example, on pin VCAP3 I measured 4.95 V and I am sure reference is fine, pin VREP it is 0 V and VCAP4 and VCAP1 are 1.2 V. By the way, communication is not working yet and I can not write on registers or at least I am not reading what I have written to them previously.

Regards,

Rashid

0 Tom Hendrick over 14 years ago in reply to Rashid Peralta

TI__Guru**** 182881 points

Hi Rashid,

Schematically, I don't see why there should be voltage problems. Check your solder joints, the orientation of the device, your supplies - all the 'usual' suspects.

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Troubles with new PCB